1. Field of the Invention
Embodiments of the invention relate to a wellhead control system for oil and gas wells. In particular, embodiments of the invention relate to systems and methods of an emergency shut down control system for surface and subsurface safety valves. Embodiments of the invention further relate to systems and methods of a relief valve control system.
2. Description of the Related Art
A wellhead system may be used to control the flow of fluids recovered from an oil and gas well in a safe and efficient manner. The wellhead system may include a variety of flow control devices, such as valves, which are operable direct fluid flow through a tubing system connected to the wellhead system. Fluids can be directed downstream of the wellhead system via the tubing system for further processing and/or storage.
The wellhead system may include surface and subsurface safety valves that are connected to the tubing system and are operable to shut off fluid flow through the tubing system in the event of an emergency in the well or at a location downstream of the wellhead system. Prior art safety valves are generally in fluid communication with the tubing system, and utilize the fluids therein for operation. For example, the pressure in the tubing system may be directly tied into the safety valves to actuate the valves into an open position, thereby allowing fluid flow through the system. In the event of an emergency, such as a rupture in the tubing system downstream of the safety valve or a drop in pressure in the well, as the pressure in the tubing system drops, so does the pressure in the safety valves. The safety valves are configured to move into a closed position after the pressure therein falls below a minimum pressure, thereby closing fluid flow through the tubing system and shutting in the wellhead system. Some safety valves may also be equipped with relief valves that are operable to block pressure from entering the valve and exhaust the pressure in the valve, thereby allowing the valve to move into a closed position.
There are numerous drawbacks to the prior art safety valve systems. One drawback includes the reliance of the safety valves on fluid pressure in the tubing system. These safety valves cannot be unilaterally operated as desired. Another drawback includes regular, manual maintenance of the safety valves to ensure that they are fully operational. Another drawback includes the potential pollution to the environment when fluid in the safety valves are exhausted into the atmosphere.
In some wellbore operations, such as when conducting a fracking operation, a high volume pressurized fluid is pumped to a manifold, which directs the fluid to one or more wells for fracturing the formation below. In the event that flow through the flow or fluid lines to the manifold and/or in the wells experience an interruption or become plugged, the highly pressurized fluid volume can cause catastrophic failure of the fluid lines, the wells, and any other equipment surrounding the wellsite, which can even potentially harm workers at the wellsite. Conventional relief valve systems are inefficient at detecting a failure, have slow response times, and/or are only one-time use, which require complete replacement in the event of operation.
Therefore, there is a need for a new and improved safety control valve system that is self reliant, can be remotely operated and monitored real-time, and can automatically shut in and/or relieve a wellhead system in the event of an emergency or when desired.